This proposal focuses on chaperone-mediated autophagy (CMA), a catabolic pathway that mediates the selective degradation of cytosolic proteins in lysosomes. CMA participates in protein quality control by degrading damaged, toxic and dysfunctional proteins. In addition to its role in protein homeostasis, recent studies in cultured cells support a role for CMA in the maintenance of the cellular energetic balance. Our lab has previously found that CMA activity decreases with age and that restoration of this type of selective autophagy in old rodents preserves proteostasis, increases resistance to stress, and improves organ function. We propose that failure of CMA with age contributes to the functional decline characteristic of old organisms and aggravates the course of age-related diseases. The goal of this proposal is to elucidate how systemic and organ-specific failure of CMA in vivo affects protein homeostasis, cellular metabolism, and ultimately impacts life- and health-span. In order to study CMA in live organisms, we have developed tissue-specific conditional knock-out mice with compromised CMA activity. This novel mouse model will enable us to investigate the consequences of CMA blockage at different ages in vivo. Using CMA-deficient animals, we will explore (1) the impact of impaired CMA on hepatic and whole-body metabolism and (2) how systemic impairment of CMA influences life-span, health-span and the rate of organ aging and how different tissues compensate for the loss of CMA. We hypothesize that CMA is functionally relevant in vivo in modulating protein quality control and energy metabolism and that these diverse functions contribute to its ability to sustain cellular health and minimize rates of organ aging. Significance: Until now, the consequences of CMA dysfunction have only been analyzed in cell culture based systems or by in vitro analyses with isolated lysosomes. By using the novel approach proposed in this application to study CMA in vivo, we will be able to translate our knowledge of the basic biology of this pathway into a physiologically relevant context. Determining how reduced CMA activity in vivo impacts proteostasis, the energetic balance, and the rate of aging will shed light on (1) the possible contribution of diminished CMA activity to age-related protein conformational disorders such as neurodegenerative disease and (2) whether reduced CMA activity partially underlies the pathogenesis of the metabolic syndrome of aging. Understanding the physiological role of CMA in vivo and the organismal response to the failure of this catabolic pathway will pave the way for future development of anti-aging strategies based on the modulation of this type of selective autophagy.